An emergency warning for a large fire burning north-east of Perth has been downgraded.

The bushfire has been burning for more than 24 hours in bushland at Bullsbrook, east of the Great Northern Highway.

On Friday night the warning was downgraded to a watch and act alert for residents at Shady Hills and west of Walyunga National Park.

Authorities warn the fire is not fully contained and there is still a possible threat to lives and homes as conditions may change.

The fire is believed to have been started by a freight train.

A community meeting on Friday has been told the fire is still very serious.

Allen Gale from the Department of Fire and Emergency Services says strong winds forecast could make the situation worse.

"Our concern is still the wind, it's just picking up a bit now and it's going to remain an easterly throughout the day and for that reason residents have been told we still can't lift that emergency warning," he said earlier on Friday.

"If the fire does jump over and start to run again in amongst that Shady Hills area and to the west of Walyunga Park then lives and property are going to be threatened directly."

Authorities will hold two community meetings on Saturday - the first at Pickett Park Hall in Bullsbrook at 10:30am, and the second at 12:00pm on the corner of Smith and Taylor roads.

About 1,460 hectares has been burnt since the fire was first reported at 11:54am (AWST) on Thursday.

Dozens of road trains are lining the road on either side of Bullsbrook as thick smoke has forced the closure of Great Northern Highway.

Authorities are considering lifting some road blocks to allow some people back into their homes in the fire-ravaged area.

Mr Gale says he understands residents are frustrated.

"We're very, very aware of the fact that there's a lot of people that aren't able to get back in, but we're hoping to be able to open up some areas and let people back to their homes shortly," he said.